Transformers
Transformers are also based on the principle that when a wire, coil or loop that is part of a circuit experiences a changing magnetic field, a voltage is induced, and a current will flow.

If two coils are near each other but NOT part of the same circuit, interesting things happen!

If the current that is applied to the input side is Alternating Current (AC) then the field of the input or primary coil will be constantly changing.
This means that the secondary or output coil will also experience a changing magnetic field, and current will flow.

There are two types of transformers.
 
A step up transformer shown above  
  • has more coils on the output or secondary coil 
  • has a higher voltage on the secondary side
  • has a lower current on the secondary side
 
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Electromagnetism
 A step down transformer shown above  
  • has more coils on the input or primary coil 
  • has a lower voltage on the secondary side
  • has a higher current on the secondary side